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New study for cationic dye removal using prepared SPGMA polymer combined with an isolated bacteria N. A. Taha1, 6, T. H. Taha2, M. A. Abu-Saied3*, M. Elsayed Youssef4, CHMELA Štefan5 1
Fabrication Technology Department, Advanced Technology and New Materials Research Institute, City for Scientific Research and Technology Applications (SRTACITY), New Borg El-Arab City 21934, Alexandria, Egypt 2
Environmental Biotechnology Department, GEBRI-Institute, City for Scientific Research and Technology Applications (SRTA-CITY), New Borg El-Arab City 21934, Alexandria, Egypt 3
Polymer Materials Research Department, Advanced Technology and New Materials Research Institute, City for Scientific Research and Technology Applications (SRTACITY), New Borg El-Arab City 21934, Alexandria, Egypt 4
Computer-Based Engineering Applications Department, Informatics Research Institute, City for Scientific Research and Technology Applications (SRTA-CITY), New Borg El-Arab City 21934, Alexandria, Egypt 5
Department of synthesis and characterization of polymers , Polymer Institute SAS, Bratislava, Slovakia 6
Chemistry Department, Al-LithUneversity College, Umm Al-Qura University, Sudia Arabia.
*Corresponding author:
[email protected] Abstract: One of the important removal methods of dye is adsorption as different types of adsorbent are used by using chemical or biological method. In this study sulphonated poly glycidylmethacrylate (SPGMA) polymer was prepared and characterized using (FTIR, TGA and SEM) to study its surface properties which can enhance the removal efficiency. Isolation and selection of bacteria was depending on its ability to form clear zones at Methylene blue containing solid agar media. The potency of dye removal was achieved by using SPGMA as adsorbent material for cationic dye removal (chemical method) and comparing the results with both of isolated bacteria (biological method) and composite of SPGMA and bacteria. Different initial concentrations of Methylene blue from 5 to 25 mg/L were used for all studied methods. The highest percentage of removal for SPGMA was at 20 mg/L after 90 min (94.8%), 95.8% at 25 mg/L after 4 h for biological method while by using composite of SPGMA and isolated bacteria the removal percentage increased to reach 96.3% at 25 mg/L. So it is recommended at higher Methylene blue concentrations to use polymer bacterial mix than using each individually. Also a mechanism of adsorption of the dye (Methylene blue) has been studied numerically by using two equilibrium isotherms (Langmuir and Freundlich). The obtained results from the above two models were validated by experimental data to investigate the effects of, temperature, initial dye concentration, and contact time. 138
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Key words: functionalization of polymer, adsorption, dye removal, mathematical Modeling Introduction: Textile industries rank first in the usage of dyes when compared to other industries like food, paper, cosmetics and carpet industries (Neill et al., 1999; Maljaei et al., 2009; Cervantes & Dos Santos, 2011). The main problem of these industries is that about 5-50% of the unfixed dyes are lost in the effluent during the dyeing process (Maljaei et al., 2009). Dyes used in textile industry may be toxic to aquatic organisms and can be resistant to natural biological degradation. Hence, the removal of synthetic organic dye stuff from waste effluents becomes environmentally important (Reffas et al., 2010). Also it is very important to treat the colored synthetic compounds as they are hazardous to human being and environments. Methylene blue dye (MB) is one of the most important synthetic dyes that can negatively affect photosynthesis. Methylene blue dye causes eye burns, and may be responsible for permanent eye injury in humans and animals. On inhalation, it can give rise to short periods of rapid or difficult breathing, while ingestion through the mouth produces a burning sensation and may cause nausea, vomiting, profuse sweating, mental confusion, painful micturition and methemoglobinemia (Reife et al., 1993; Douglas et al., 1984; Kannan & Sundaram, 2001). Therefore, the treatment of effluent containing such dyes is of interest due to its esthetic impact on receiving waters. There are several methods used to treat wastewaters which contain organic pollutants and dyes. These methods include physical, chemical and biological processes, such as chemical coagulation (Moghaddam et al., 2010), ozonation (Oguz et al., 2005; Tapalad et al., 2008) and adsorption (Hashemian et al., 2007; Hashemian et al., 2008). Adsorption has been proven to be an excellent way of treating textile waste effluents, offering significant advantages, such as low cost, availability, profitability, ease of operation and efficiency over many conventional methods, especially from an economical and environmental point of view (Ravikumar et al., 2005; Allen et al., 2005; Arami et al., 2005; Mittal et al., 2005). Also Adsorption technology is one of the widely used treatment technologies to remove synthetic dyes from wastewater because of the negligible one-time investment, separation easy and use-conveniently (Asgher & Bhatti, 2012). On the other hand, several attempts have been developed to use microbes like bacteria and fungi for biodegradation and decolorization of water contaminated dyes (Hafshejani, et al., 2013). (Albadarin et al., 2014) have investigated the effectiveness of using the mixture of tea waste and dolomite as adsorbents for the removal of copper and Methylene blue from aqueous solutions. The results showed that mixed of tea waste and dolomite can simultaneously be commendably used to treat aqueous solutions from copper and Methylene blue. (Banerjee et al., 2014) have studied numerically how to remove Methylene blue from aqueous solutions via an activated fly ash (AFSH). The numerical results of (kinetic and equilibrium isotherms as well as thermodynamic implemented models) showed a high potential for adsorption of Methylene blue (MB) from aqueous solutions by acid activated fly ash (AFSH). The amount of dye removed increase with an increase in initial dye concentration, contact time while it decreases with increase in temperature and, for pH was found (pH 8.09.0) optimum for maximum MB removal. (Chen et al., 2011) have found the possible use of silkworm exuviate west as a bio-sorbent for the efficient treatment aqueous solutions from dye (Methylene blue). The overall results showed that the silkworm 139
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exuviate west is an effective and low-cost bio-sorbent for west water treatment particularly the removal of Methylene blue from aqueous solutions. (Roman Bochenek, et al., 2011) has well-thought-out the ion exchange processas the wastewater treatment mechanism for continuous processes. The best results in terms of the process performance were achieved in case of optimization of the operating conditions for the columns operating jointly in the purification node. The optimization results indicated that continuous process can significantly outperform the periodic operation. (Yu & Luo, 2002) have proven that a three-phase fluidized bed can be used in ultra-pure water supply to a power plant. Cationic ion exchange and bicarbonate removal can be treated simultaneously in a counter- current three-phase fluidized bed when cationic ion-exchange resin as solid phase was used. (Gürses et al., 2014) have studied the opportunity to remove dye (Methylene blue) from aqueous solution by untreated lignite as potential low-cost adsorbent. Kinetic, thermodynamic and equilibrium approach have been investigated the effectiveness of using untreated lignite as dye adsorbent. The results showed that the concentration, temperature and ionic strength have not significant affect by different stirring speeds. This research target was concerned from one side with the isolation of bacterial isolate able to degrade and decolorize Methylene blue dyes effectively and from the other side comparing the effectiveness of Methylene blue decolorization with our prepared polymer (SPGMA) and bacterial isolate both solitary and in-combination. To study the capability to model the equilibrium adsorption data, both two –parameter model isotherms, Langmuir and Freundlish isotherms have been investigated. The related parameters that affect dye removal such as, initial dye concentration, adsorption temperature and adsorption duration were widely studied. EXPERIMENTAL Materials Glycidyl methacrylate (GMA; 97%) from Sigma-Aldrich Chemicals (Switzerland), Ethyl alcohol absolute (99%) and Sodium sulfite (SS) (Sigma-Aldrich Chemicals), Ltd. (Germany). Methylene blue was obtained from NICE chemicals pvt. Ltd company and local Egyptian soil samples for bacterial isolation were collected from New Borg El-Arab city, Alexandria. Methods 1- Photo Initiated Atom Transfer Radical Polymerization (ATRP) of Glycidyl Methacrylate (GMA) in Anizole General procedure for photo ATRP of GMA was as follows. To a 10 ml Schlenk tube containing CuBr2 and TPMA, evacuated and filled with argon. Argonpurged anisole was added under argon atmosphere. The mixture in the Schlenk tube was sonicated for 5 min to form a CuBr2/TPMA complex. Subsequently GMA purged with argon and BPN was added to the Schlenk tube under argon atmosphere. The mixture was degassed by three freeze-pump-thaw cycles and backfilled with argon. Photo polymerization with light of λ > 350 nm was performed using a mediumpressure mercury lamp in a Spectromat apparatus (Ivoclar AG, Lichtenstein, glass filter λ = 350-550 nm). To prevent heating of the sample during irradiation, the 140
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Schlenk tube was placed into a double-layer glass tube. In the outer layer of the finger, water thermo stated to 25°C was circulated. 2- sulphonation process The epoxy groups of PGMA chains were reacted with sodium sulphite, dissolved in alcoholic aqueous solution at 80°C for 2 h. The excess of sodium sulphite solution was discharged after centrifugation at 14,000 rpm for 30 min using ultra speed centrifuge then washing using distilled water to remove any un-reacted sodium sulphite (Mohy‐Eldin et al.,2009; Elkady et al., 2011; Abu-Saied et al, 2013; Mohy Eldin et al., 2010). 3- Preparation of Methylene Blue solution Methylene blue powder (MB) was dried at 110°C for 2 hr before use. The stock solution of 1000 mg/L was prepared by dissolving 1.00 g of MB in 1000 ml distilled water. The experimental solutions with different concentrations were prepared by diluting the stock solution with distilled water. 4- Batch equilibrium studies Kinetic adsorption experiments were carried out to study the effect of time on adsorption process. Adsorption tests were performed in a set of Erlenmeyer flasks (250 ml) where 50 ml of Methylene blue solutions with initial concentrations of 5-25 mg/L were placed in these flasks. Equal mass of 0.1 g of the prepared poly glycidyl methacrylate (PGMA) was added to each flask and kept in an orbital shaker operated at 200 rpm at ambient temperature (± 25ᵒC). The dye concentration was analyzed using UV/VIS spectrophotometer (Ultrospec 2000 - Pharmacia Biotech), the sample was separated by decantation. All the measurements were doneat wave length corresponding to the maximum absorbance of 655 nm. The dye removal percentage can be calculated as follows: 𝑅𝑒𝑚𝑜𝑣𝑎𝑙 𝑝𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒 =
Co − Ce ∗ 100 Co
(1)
WhereC0 and Ce (mg/L) are the liquid-phase concentrations of dye at initial and equilibrium, respectively. 5- Isolation of Methylene blue decolorizing bacteria Local Egyptian soil samples were collected from Borg El-Arab city, Alexandria and were submitted to serial dilutions (10-1-10-5). One hundred micro liter of each dilution was spread over nutrient agar (NA) plates containing 10 mg/L Methylene blue and were incubated at 30oC for 5 days. The colonies that appeared clear zones around their margins were picked out and checked for their purification on new sterile nutrient agar plates. The purified bacterial isolates were later preserved in 60% glycerol and kept at- 80oC. 6- Screening and selection of the best dye decolorizing bacteria The assumed dye decolorizing bacteria were submitted for cultivation in Methylene blue containing broth in order to choose the best dye decolorizing one. Fifty ml of nutrient broth that contains 10 mg/L Methylene blue were sterilized in 250 ml flasks and were inoculated with 50 µl of 18 h overnight cultures of each tested 141
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bacteria. One of the flasks were kept without inoculation and used as the control sample. The flasks were incubated in shaker incubator at 30oC and 150 rpm for three days. Ten ml of each bacterial broth were centrifuged at 10000 rpm for 10 min and the optical density of the supernatants was measured against the control sample at 655 nm. The percentage of dye removal was calculated for each bacteria isolate in comparison with optical density for the control sample. 7- Percentage of decolorization at different concentrations of Methylene blue The best decolorizing bacterial isolate was chosen to be tested for its ability to decolorize different concentrations of the tested dye. To achieve this target, 100 µl overnight culture of the selected isolate was inoculated into fifty ml of five nutrient broth containing flasks. The flasks were incubated at 30oC and 150 rpm for 18 h to allow the bacterial isolate to enter the log phase. Different concentrations (5, 10, 15, 20 and 25 mg/L) of Methylene blue were added to each flask separately. The flasks were incubated back again at the same mentioned incubation conditions and one ml sample was regularly withdrawn every 30 min for 5 h. The collected samples were centrifuged at 10000 rpm for 10 min and the optical density of the supernatants was measured at 655 nm. The percentage of dye removal at each concentration was also calculated in comparison with optical density for the control sample for each concentration. 8-
Efficiency of bio-decolorization at the presence of Sulphonated poly Glycidyl methacrylate
In a trial to improve the bacterial bio-removal of Methylene blue, certain weights of the Sulphonated poly glycidyl methacrylate were added together to the bacterial experiment as will be explained. Fifty milliliter of nutrient broth (pH 7.0 ±2) were sterilized and inoculated with 100 µl of 18 h overnight culture of the tested bacteria and incubated at 30oC and 150 rpm for 18 h. After the incubation period, 1% w/v of GMA polymer was added to each flask separately. The polymer addition was followed by addition of the tested Methylene blue dye in different and separate concentrations (5, 10, 15, 20 and 25 mg/L). After re-incubation, the samples were also withdrawn every 30 min, centrifuged at 10000 rpm for 10 min and the optical density was measured at 655 nm as mentioned before. The percentage of dye removal at each concentration was also calculated in comparison with optical density of each control sample. Identification of the bacterial isolate DNA extraction The genomic DNA from the bacterial isolate was extracted using Bacterial genomic DNA extraction kit (Promega, USA) according to the manufacturer instructions. Amplification and sequencing of 16S rRNA gene The 16S rRNA gene was amplified using universal primers according to (Suganya, et al., 2013) with some modifications. The used forward and reverse primers were able to amplify almost 1500 pb of the required gene. The sequence for the 16S forward primer (27F) was 5' AGAGTTTGATCMTGGCTCAG-3' and the 142
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sequence for the reverse primer (1492R) was 5'-TACGGYTACCTTGTTACGACTT3'. The PCR mixture consisted of 10 picomoles of each primer, 1μl of chromosomal DNA, 0.5μl of dNTPs and 2.5 units of Taq polymerase with 10μl of polymerase buffer containing MgCl2. The PCR was carried out with starting denaturation step at 95oC for 10 min followed by 30 cycles of 94ºC for 1 min, 55ºC for 1 min and 72ºC for 2 min followed by final extension step at 72oC for 10 min. After completion, a fraction of the PCR mixture was examined using 1.5% agarose gel in TBE buffer (pH 8.5). Electrophoresis was carried out for 20 min at 150V and the formed PCR band was visualized using UV trans-illuminator. The obtained gene was purified using PCR gel purification kit (Promega, USA) and was submitted to sequencing (Sigma, Germany) and the similarity of the obtained sequence was matched with the Gen Bank deposited sequences (www.ncbi.nlm.nih.gov). Characterization Infrared spectrophotometric analysis Functional groups investigation in both poly glycidylmethacrylate and Sulphonated poly Glycidyl methacrylate having different GPs was carried out using Fourier transform infrared spectrophotometer (Shimadzu FTIR-8400 S, Japan). Thermogravimetric analysis Thermal stability of poly glycidyl methacrylate and Sulphonated poly glycidyl methacrylate was studied by using thermogravimetric analyzer (Shimadzu TGA-50, Japan) under nitrogen atmosphere at a heating rate of 10°C/min. Scanning electron microscopic analysis Surface characterization of poly Glycidyl methacrylate and Sulphonated poly Glycidyl methacrylate was carried out using energy-dispersive analysis Joel Jsm 6360LA, Japan). Mathematical model Adsorbed dye and percentage of removal of Methylene Blue were calculated using the following equations 2 and 3. 𝑉 𝑀
(2)
𝐶𝑜 − 𝐶𝑒 × 100 𝐶𝑜
(3)
𝑞𝑒 = (𝐶𝑜 − 𝐶𝑒 ) % 𝑅𝑒𝑚𝑜𝑣𝑎𝑙 =
Where 𝑞𝑒 Adsorbed dye [mg/g], 𝐶𝑜 and 𝐶𝑒 initial and equilibrium MB concentration [mg/L], 𝑉 solution volume, 𝑀 mass of adsorbent. Adsorption isotherm studies The Freundlich isotherm and Langmuir isotherm were used to predict the mechanism of adsorption process. The Freundlich isotherm The main assumption in Freundlich isotherm is that sorption process occurred in a heterogeneous layer which can be expressed in equation 4 and 5. 143
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1 log(𝑞𝑒 ) = log(𝐾𝑓 ) + log(𝐶𝑒 ) 𝑛 1 𝑞𝑒 = 𝐾𝑓 𝐶𝑒𝑛
(4) (5)
1
Where 𝐾𝑓 Freundlich constant and 𝑛 intensity of adsorption. The Langmuir isotherm The main assumption in Langmuir isotherm is that fixed number of adsorption sites are available on the surface of solid which can be expressed in equation 6 and 7. 1 1 1 = + 𝑞𝑒 𝑞𝑚 𝐾𝑎 𝑞𝑚 𝐶𝑒 𝑞𝑒 =
(6)
𝑞𝑚 𝐾𝑎 𝐶𝑒 1 + 𝐾𝑎 𝐶𝑒
(7)
Adsorption kinetics studies The pseudo first order equation as followed in equation 8 and 9. The pseudo second order equation (equation 10 and 11).
log(𝑞𝑒 − 𝑞) = log(𝑞𝑒 ) −
𝐾1 𝑡 2.303
(8)
𝑞 = 𝑞𝑒 (1 − 𝑒 −𝐾1 𝑡 )
(9)
𝑡 1 1 = + 𝑡 𝑞 𝐾2 𝑞𝑒 2 𝑞𝑒
(10)
𝑞=
𝐾2 𝑞𝑒 2 𝑡 1 + 𝐾2 𝑞𝑒 𝑡
(11)
Where 𝐾1 the pseudo first order adsorption rate constant, t is time, 𝐾2 the pseudo second order adsorption rate constant.
Adsorption thermodynamics studies Thermodynamic parameters which calculate MB adsorption are ∆𝐺 𝑜 (free energy change), ∆𝑆 𝑜 (change in entropy) and ∆𝐻 𝑜 (change in enthalpy). ∆𝐺 𝑜 = −𝑅𝑇 ln(𝐾𝑑 )
(12)
∆𝑆 𝑜 ∆𝐻 𝑜 ln(𝐾𝑑 ) = − 𝑅 𝑅𝑇
(13)
Where 𝐾𝑑 distribution coefficient, T is temperature and R gas constant. 144
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Results and discussion: (1)Characterization of the synthesized Sulphonated poly glycidyl methacrylate (SPGMA) a- Infrared spectrophotometric analysis The FT-IR spectra of PGMA (Figure 1) showed the absorption bands at 1725, 1300–1100 cm−1, caused by the stretching vibration of the ester carbonyl groups, CO-C stretching in addition to the characteristic bands of the epoxy ring at 1260 and 950–815 cm−1(Bondar et al,2004). After performing sulphonation process, absorption bands of the epoxy rings at 1260 cm−1 start to disappear, while the band at 760 cm−1 of weak intensity still noticed with shift to 780 cm−1. This may be referred to a minor fraction of epoxy rings that may have taken part in the formation of cross-linking structure during polymerization (Evtushenko et al., 1990). The characteristic absorption band of the sulphonic group at 1050–1060 cm−1 was recognized for sulphonated samples. Since the epoxy groups in poly (GMA) reacted with Na2SO3 to form PGMA-SO3Na, the epoxy groups would produce -OH groups. The illustrated data have verified the occurrence of the sulphonation process.
Figure 1; FT-IR spectrum of PGMA (M) and sulphonated PGMA (SM). b- Thermogravimetric analysis In addition, TGA thermo-grams (Figure 2) showed the weight loss of samples at 120°C, due to water evaporation. Samples treated with sodium sulphite do not show a significant increase in weight loss. A remarkable thermal stability was observed for the sulphonated samples. Positive shift of characteristic thermogramof PGMA starting at 240°C to higher temperature range 260–280°C was recognized. At 300°C, the 145
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PGMA sample lost about 45% of its weight. Sulphonated samples at the same temperature showed a reduction in weight loss 7.5%. This result also means that data have verified the occurrence of the sulphonation process.
Figure 2; TGA thermogramsof PGMA and sulphonated PGMA (SM). c- Scanning Electron Microscopic (SEM) analysis Different SEM images with different magnification factors had been used to illustrate the actual presence or absence of sulphonic group. Figure 3(A, B and C) display SEM pictures for PGMA while figure 3 (D, E and F) for sulphonated PGMA where an obvious heterogeneous morphology was noticed. It’s clear from the Figures that the changes in structure of particles as a result of the modification sulphonation process have been proved.
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Figure 3; SEM Micrograph of: (A 500X, B 5000X and C 10000X) display SEM pictures for PGMA and (D 500X, E 5000X and F 10000X) for sulphonated PGMA. (2)Isolation of Methylene blue decolorizing bacteria Five bacterial isolates labeled as MB1, MB2, MB3, MB4 and S1 were able to form clear zones around their colonies at Methylene blue containing nutrient agar plates. To assure the ability of the bacterial isolates to decolorize the dye at liquid medium, the five isolates were grown in nutrient broth contains 10 mg/L Methylene blue. The percentage of removal was varied among the bacterial isolates as recorded through the measured optical density. It had been shown that, the percentage of dye removal ranged from 3 to 38% after 3 days of incubation. The best recorded percentage was combined with MB2 isolate as shown in figure 4. 147
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40 35
% Removal
30 25 20 15 10 5 0 MB1
MB2
MB3
MB4
S1
Bacterial Isolates
Figure 4; Comparison between the bacterial isolates that were able to decolorize Methylene blue after three days of incubation. (3)Identification of the bacterial isolate using 16S rRNA sequencing The molecular identification of bacterial isolates is efficiently supported by the 16S rRNA amplification and sequencing (Suganya, et al., 2013). Our bacterial isolate was submitted to genomic DNA extraction followed by PCR amplification of 16S rRNA gene using universal primers. The primers were able to amplify 1500 pb length of the specified gene as shown in figure 5. The obtained gene sequence was compared with GenBank data base where the bacterial isolate was highly similar to Bacillus thuringiensis with 98% percentage of similarity. The bacterial isolate was re-named as Bacillus thuringiensis MB2 TMN and the multiple sequence alignment, molecular phylogeny and phylogenetic tree were performed using MEGA 5 software as shown in figure 6.
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Figure 5; PCR amplification of 1500 pb of 16S rRNA using universal primers. M: 1kb DNA ladder; MB2: amplified 16S rRNA gene of isolate MB2. HF584912.1| B. thuringiensis gb|KJ943977.1| Bacillus sp. HF585010.1| B. thuringiensis Bacillus thuringiensis MB2 TMN gb|KJ524505.1| B. cereus gb|JX280922.1| B. thuringiensis gb|KJ878595.1| Bacillus sp. gb|KC508632.1| Bacillus sp. gb|KJ734022.1| Bacillus sp. gb|J01859.1|E. coli gb|KJ944013.1| Bacillus sp. gb|KC857472.1| Bacillus sp. gb|JX994097.1| B. thuringiensis gb|KJ716488.1| B. thuringiensis
2.5
2.0
1.5
1.0
0.5
0.0
Figure 6; phylogenetic tree of 16S rRNA gene of Bacillus thuringiensis isolate with related strains.
(4)Study of decolorization percentage at different concentrations of Methylene blue The best selected bacterial isolate was checked for its ability to decolorize high concentrations of the dye. It had been showed that, the bacterial isolate was able to degrade or decolorize all the tested Methylene blue concentrations ranged from 5 to 25 mg/L successfully. Results revealed that, MB2 isolate could decolorize high concentrations of the dye more effectively than the lower concentrations. The MB2 149
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isolate was able to decolorize up to 95.8 % of Methylene blue at 25 mg/L compared with 87.9 % at 5 mg/L through 4 and 1.5 hour respectively (figure 7). Results showed that, although MB2 isolate can effectively decolorize high concentrations of Methylene blue than lower ones, it seems that higher concentrations are more toxic to the bacterial isolate compared to the lower concentrations. This notice could be deduced as follows: at 5, 10 and 15 mg/L, MB2 isolate could easily start the decolorization process from the zero time with percentage of removal ranged from 50 to 64.5 %. The bacterial isolate was able to decolorize Methylene blue with percentage of removal ranged from 87.9 to 94.4 % within 1 hour or less according to the dye concentration. As shown in figure 7, at 5 mg/L the MB2 isolate was able to reach the maximum percentage of removal after 0.5 h; however it took 1 hour to reach maximum percentage of removal at 10 and 15 mg/L. On the other hand, at higher concentrations of Methylene blue, MB2 isolate took from 2 to 3 hours to reach the maximum percentage of removal at 20 and 25 mg/L. These results indicates that, higher concentrations of Methylene blue are more toxic to the isolate than the lower ones and hence the bacterial isolate would need more time to be adapted for these toxic concentrations. 5 mg/l
10 mg/l
15 mg/l
20 mg/l
25 mg/l
100
% Removal
90 80 70 60
50 40 0
1
2
3
4
Time (Hours)
Figure 7; Bio-removal of Methylene blue by MB2 bacterial isolate at 5, 10, 15, 20 and 25 mg/L.
(5)Effect of contact time and initial dye concentration on adsorption equilibrium: Figure 8 showed the adsorption of MB on PGMA at different initial concentrations ranged from (5-25 mg/L), which studied as a function of contact time ranging from 590 min in order to determine the equilibrium time. The figure showed that the dye uptake increased with time and reached a constant value where no more dye was removed from the solution. At this point, the amount of dye being adsorbed onto the adsorbent was in a state of dynamic equilibrium with the amount of dye desorbed from the adsorbent. The time required to attain this state of equilibrium was termed the equilibrium time and the amount of dye adsorbed at the equilibrium time reflected the maximum dye adsorption capacity of the adsorbent under these particular conditions. It indicated that the contact time needed for MB solutions with initial 150
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concentrations of 5-25 mg/L to reach equilibrium was 45 min. However, the experimental data were measured at 90 min to make sure that full equilibrium was attained. The rapid adsorption observed during the first 20 min is probably due to the abundant availability of active sites on the adsorbent surface, and with the gradual occupancy of these sites, the sorption becomes less efficient, also by increasing MB concentration the percentage removal increase to reach 94.8 % after 90 min for 20 mg/L dye concentration. 120 100
% Re
80 60
5 mg/l 10 mg/l 15 mg/l 20 mg/l 25 mg/l
40 20 0 0
10
20
30
40
50
60
70
80
90
100
Time, min
Figure 8; Influence of dye concentration on adsorption of MB by SPGMA
(6)Bio-removal of Methylene blue at the presence of bacteria and polymer According to the data depicted in figure 9, it was observed that both of chemical and biological methods can efficiently remove and decolorize the tested dye. The recorded results were varied according to the dye concentration. At the lowest concentration (5 mg/L), the chemical methods showed more effective percentage of removal compared with composite and biological one. It was observed that the biological method recorded lower percentage of removal than the chemical method but higher than the composite. The polymer alone was able to remove (90 %), while both of bacterial isolate and polymer-bacterial mix were able to remove (88 and 84 %) respectively. The recorded results were slightly differ at 10 mg/L Methylene blue; where, the highest dye removal was achieved by (92 %) with the bacterial isolate alone, while both of polymer and polymer-bacterial mix have the same removal percentage by (91 %). At the consequence concentrations of the dye, 15, 20 and 25 mg/L, the results were completely differ than those recorded for the lower dye concentrations. The order of efficiency of dye removal was polymer
